The enzyme DAPA aminotransferase which catalyzes the following reaction: 7-keto-8-aminopelargonic acid plus S-adenosylmethionine yields 7,8, diaminopelargonic acid has been purified 2,000 fold. The enzyme is a dimer with a molecular weight of 83,000. The kinetic studies show a ping pong mechanism. The keto product has yet to be isolated. Biotin analogues, alpha-dehydrobiotin and homobiotin, repress the biotin operon but are not as effective as biotin. Alpha- methyldesthiobiotin is a competitive inhibitor of desthiobiotin in its conversion to biotin.